And before you complain about that being a much bigger area, here's the land area for metro Detroit compared to some of China's biggest cities:
Detroit metro: 1,337.1 sq mi
Guangzhou Urban: 1,483.95 sq mi / ~11 million
Shanghai Urban: 1,550 sq mi / ~24 million
Chengdu Urban: 1,760.0 sq mi / ~11 million
Chinese cities typically have boundaries roughly equivalent to US metro areas. They certainly have larger populations than Detroit, but not as much as you guys think.
[1]https://en.wikipedia.org/wiki/Metro_Detroit
[2]https://en.wikipedia.org/wiki/Guangzhou
But given the unique situation of Detroit, and the fact that US cities are generally organized in quite a different fashion to Chinese cities there's really no good use in comparing the two IMO.
Then it fell to a 0.7M population.
When your city infrastructure and services are sized for 2 to 3 times your population, said population cannot sustain these infrastructure and services, and it's also really difficult to scale down these.
This is in sharp contrast with Chinese cities that are nearly all growing at a fast rate, maybe too fast in fact.
I'm aware it's an over simplification, but it illustrates the twos are not really comparable.